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Pulse radar systemPulse radar system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070024493, Pulse radar system. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a pulse radar system using a millimeter wave band or a quasi-millimeter wave band, and particularly to a pulse radar system having improvements in distance resolution with respect to a reflective wave from objects in a short distance. [0003] 2. Description of the Related Art [0004] Recently, a pulse radar system is used with the purpose of collision avoidance or auto clews. The round-trip distance to an object can be found by multiplying the time that elapses between the radiation of a transmission pulse and the receipt of a reception pulse wave reflected from the object, by light velocity. Consequently, the pulse radar system is intended for calculating the distance to the object by measuring the time that elapses between the radiation of the transmission pulse wave and the receipt of the reception pulse wave from the object. [0005] In this pulse radar system, the transmission pulse wave is radiated, followed by preparation for receiving the reception pulse wave reflected from the object in a short distance. The pulse radar system with the purpose of collision avoidance or auto clews demands exact detection of the positions of objects in a wide range of from tens of centimeters to tens of meters. [0006] When detecting the positions of two or more objects adjacent to each other, the reflected waves from the different objects reach the pulse radar system at substantially the same time. Therefore, in the conventional method for detecting the positions of different objects, the pulse width of a transmission pulse wave is reduced so as to eliminate overlapping between reception pulse waves from the different objects, thereby increasing distance resolution between those objects (for example, refer to Japanese Unexamined Patent Publication No. 6-249943). SUMMARY OF THE INVENTION [0007] Nevertheless, with the method for increasing distance resolution by using a short pulse, a pulse width of 3 nsec or less is needed for detecting two obstacles one meter apart. That is, transmission pulses are reflected from the two obstacles, respectively, so that the time between these reflected waves is 3 nsec or less. It is therefore necessary to perform sequentially signal processing of their respective reception pulses (for example, when performing signal processing of A/D (analog-digital) conversion) in time intervals as short as 3 nsec. This requires a high-speed circuit, and increases signal processing circuit load. [0008] Reductions in pulse width can improve electrical performance, whereas the signal bandwidth after demodulation is increased, necessitating an amplifier that is wide in the required bandwidth of an intermediate frequency stage. It is difficult to design a wideband amplifier, and handling of pulse-shaped waveforms requires flattening of group delay characteristic, resulting in high costs. [0009] Consequently, the distance resolution improvement with the reductions in pulse width has a limit. [0010] It is desirable to provide a pulse radar system capable of improving distance resolution between objects without requiring speed-up of a reception circuit. [0011] To this end, a reception pulse is extracted in synchronization with a gate pulse having a cycle which is a rational multiple of a cycle of a transmission pulse and is different from the cycle of the transmission pulse. [0012] According to an embodiment of the present invention, there is provided a pulse radar system including: a pulse output circuit outputting a periodic transmission pulse and a gate pulse, the gate pulse having a cycle which is a rational multiple of a cycle of the transmission pulse and is different from the cycle of the transmission pulse; a transmission circuit generating a transmission pulse wave based on a transmission pulse from the pulse output circuit, and outputting the transmission pulse wave generated; a transmission antenna radiating a transmission pulse wave from the transmission circuit; a reception antenna receiving a reception pulse wave, the reception pulse wave being radiated from the transmission antenna as a transmission pulse wave and reflected from an object; a reception circuit demodulating the reception pulse wave from the reception antenna and outputting a reception pulse; and an extracting circuit extracting a reception pulse, which is synchronized with a gate pulse from the pulse output circuit, from among reception pulses from the reception circuit, and outputting the reception pulse extracted. [0013] By extracting the reception pulse that synchronizes with the gate pulse having a cycle which is a rational multiple of a cycle of a transmission pulse and is different from the cycle of the transmission pulse, a time base can be expanded to improve distance resolution between objects without requiring speed-up of the reception circuit. [0014] Preferably, in the above pulse radar system, the pulse output circuit can change the ratio between a cycle of the transmission pulse and a cycle of the gate pulse. [0015] This provides a variable rate of time base expansion, making it possible to select freely distance resolution between objects. [0016] Preferably, in the pulse radar system, the pulse output circuit can change a relative phase between the transmission pulse and the gate pulse. [0017] This permits extraction of a reception pulse in a specific position. Hence, the time base can be shifted by changing the ratio between a cycle of the transmission pulse and a cycle of the gate pulse, and by changing the relative phase between the transmission pulse and the gate pulse. It is therefore possible to extract a reception pulse in a specific position, and select freely a detecting position of the objects on the time base. [0018] Preferably, the pulse radar system is further provided with a distance calculating circuit calculating a distance to the object, based on an elapsed time from when a transmission pulse which immediately precedes a reception pulse extracted by the extracting circuit is outputted from the pulse output circuit until the reception pulse is outputted from the extracting circuit. [0019] This enables calculation of the distances to the objects. [0020] Preferably, the pulse radar system is further provided with a distance calculating circuit calculating a distance to the object based on an elapsed time, a phase of a transmission pulse outputted from the pulse output circuit and a cycle of the transmission pulse at the time when the reception pulse is outputted from the extracting circuit, the elapsed time being from when a transmission pulse is outputted from the pulse output circuit until a reception pulse is outputted from the extracting circuit. [0021] This permits calculation of the distances to the objects. [0022] Preferably, in the pulse radar system, the extracting circuit is configured as a single balanced mixer taking in the gate pulse from the pulse output circuit as a balanced input, and finding a product of the gate pulse and the reception pulse from the reception circuit. Continue reading about Pulse radar system... Full patent description for Pulse radar system Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Pulse radar system patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Pulse radar system or other areas of interest. ### Previous Patent Application: Car reversing radar sensor having fine-tuning feature Next Patent Application: Radar signal processor Industry Class: Communications: directive radio wave systems and devices (e.g., radar, radio navigation) ### FreshPatents.com Support Thank you for viewing the Pulse radar system patent info. 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